Hi Dan, The fibre loop is a data point. So the AsBuiltLength represents the difference between begin and endmeasure. I want to add an algorithm to the AsBuiltLength field: AsBuiltLength = endmeasure -beginmeasure [or vice versa]. This will save a bit of time. Cheers, Sean

I take it you aren't using arcmap which would be a simple field calculation, so perhaps you might want to elaborate on which part of the 'Developer' forest you are in. You can Share to a more directed space if you want (access to the top right of your question)

and Pythagorean theorem to the rescue... assuming you can calculate the difference in the x and y coordinates from the fields. If you don't have them, then you can actually calculate the same values using the field calculator and retrieving the start and end points using arcpy in the field calculator.